Arc tube mounting within vitreous outer envelope

ABSTRACT

A high intensity jacketed discharge lamp wherein the arc tube is supported within the outer jacket by a divided mount. The mount section at each end of the arc tube comprises a metal band clamped around the wide pinch seal to which short support rods are attached. The pinch seals have blind notches in their ends which accommodate the ends of right angle braces attached to the rods. The combination of bands and braces assures the required longitudinal rigidity in the mount coupled with sufficient play to withstand shock.   D R A W I N G

United States Patent Leonard F. Kramel East Cleveland;

Stanley D. Tabor, Jr., Cleveland, Ohio 744,756

July 15 1968 Jan. 26, 1971 General Electric Company a corporation of New York Inventors Appl. No. Filed Patented Assignee ARC TUBE MOUNTING WITHIN VITREOUS OUTER ENVELOPE 2 Claims, 3 Drawing Figs.

US. Cl 313/25, 313/184, 313/324 Int. Cl ..I-l01j 61/12, H01 j 61/52 Field of Search 313/25, 184, 3l2, 318, 324

[56] References Cited UNITED STATES PATENTS 2,733,363 l/1956 Dell 313/184X 2,904,710 9/1959 Beeninga et al. 313/184X 2,918,592 12/1959 Pomfrett et al. 313/25 3,424,935 l/1969 Gungle et al 313/184X Primary Examiner-John Kominski Assistant Examiner-Palmer C Demeo Attorneys-Ernest W. Legree, Henry P. Truesdell, Frank L. Neuhauser, Oscar B. Waddell and Melvin M. Goldenberg ABSTRACT: A high intensity jacketed discharge lamp wherein the arc tube is supported within the outer jacket by a divided mount. The mount section at each end of the arc tube comprises a metal band clamped around the wide pinch seal to which short support rods are attached. The pinch seals have blind notches in their ends which accommodate the ends of right angle braces attached to the rods. The combination of bands and braces assures the required longitudinal rigidity in the mount coupled with sufficient play to withstand shock.

PATENTEU JAN28 l97| Inven tors: Leonard F. Kvamel,

S tanLe D. TaboT Jr of Their A t car-neg ARC TUBE MOUNTING WITHIN VITREOUS OUTER ENVELOPE BACKGROUND OF THE INVENTION The invention relates to electric discharge lamps of the high pressure metal vapor type having an arc tube mounted in a vitreous outer envelope or jacket and is more particularly concerned with the mounting of the arc tube in the jacket.

High intensity metal vapor lamps commercially known at the present time include high pressure mercury and mercurymetal halide lamps. Such lamps comprise a quartz arc tube enclosed in a vitreous outer envelope or jacket provided with a screw base at one end. The are tube contains a quantity of mercury along with an inert starting gas such as argon and is provided with activated thermionic electrodes at opposite ends. The mercury-metal halide lamp also contains one or more metal halides such as sodium, thallium and indium iodides, in addition to the mercury and starting gas. The space between the are tube and the outer envelope or, jacket may be either evacuated or filled with an inert gas such as nitrogen.

SUMMARY OF THE INVENTION It is desirable to provide a mounting arrangement for the arc tube which causes minimal absorption of light or obstruction of radiation including ultraviolet radiation and which is at the same time rugged and economical, to manufacture. Any obstruction of light or radiation means loss or inefficient use of energy and should be eliminated whenever possible.

In US. Pat. No. 2,888,585, Martt et al., an integral mount is disclosed which eliminates the long side rods extending parallel to the arc tube by providing support wires or dummy leads in the corners of the pinch seals which serve as integral mount supports. Four such dummy leads are provided, one in each corner of the pinch seals at each end of the arc tube, and these provide the entire support for the arc tube. While this construction is optimum from the point of view of minimizing the obstruction of light or absorption of radiation from the arc tube, it is not sufficiently rugged and shock-resistant for some applications encountered in service. The object of the invention is to provide a new and improved mounting overcoming those drawbacks.

In accordance with the invention, a divided mount is used in which the mount section at each end of the arc tube comprises a metal band clamped aroundthe wide pinch seal to which short axially extending support rods are attached, and the mount section is braced-by lateral rod braces extending from the support rods into engagement with the end of the pinch seal.

In a preferred embodiment, the pinch seal is provided with blind notches in its end which accommodate the ends of rightangle rod braces attached to the support rods. The notches prevent the band from sliding outward off the pinch seal and the braces prevent it from sliding inward. One pair of support rods is fastened to a stiff inlead wire passing through the stem of the outer jacket. The other pair of support rods has a resilient engagement with the outer or dome end of the outer jacket. The bands and braces are particularly effective in preventing sideways displacement or cocking of the arc tube relative to the divided mount sections as might otherwise happen upon a blow to the lamp in-the plane of the pinch seals. The combination assures the required longitudinal rigidity to the arc tube mount assembly, while preserving sufficient play in the parts to accommodate heat expansion and withstand the abuse of handling and service use.

DESCRIPTION OF DRAWINGS FIG. 1 is a front elevation view of a high intensity mercury metal vapor arc lamp provided with a divided frame mount embodying the invention.

FIG. 2 is an end view of the mount of FIG. 1 as seen looking up at section 22.

FIG. 3 is a simplified fragmentary line drawing of the lampillustrating cocking of the arc tube.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawing and FIG. I in particular. there is shown a high pressure mercury metal halide vapor lamp 1 comprising an outer vitreous envelope or jacket 2 having a central bulbous portion 3 and tubular ends 4, 5. The bulbous shape assures a sufficiently low temperature of the glass jacket in the vicinity of the arc tube where it tends to be highest. The jacket is provided at its upper or base end with a reentrant stem 6 having a press 7 through which extend relatively stiff inlead wires 8, 9 connected at their outer ends to the contacts of the usual screw type base, namely the threaded shell 10 and the insulated center contact 1 I.

The inner arc tube 12 is made of quartz and has sealed therein at opposite ends a pair of main discharge supporting electrodes 13, 14 supported on inleads l5, 16 which constitute the arc tube terminals. The electrode inleads include intermediate thin molybdenum foil sections which are hermetically sealed through full diameter pinch seals 17, I8 at the ends of the arc tube. The main electrodes I3, 14 each comprise a double layer tungsten wire helix wrapped around a tungsten core wire. In the inner layer of the helix the turns are spaced apart leaving gaps or interstices between them which are covered by the closely spaced turns of the outer layer. The main electrodes are activated by thorium oxide coating the turns of the helix and filling the interstices between the turns. An auxiliary starting electrode 19 is provided at the base end of the arc tube and consists merely of the inwardly projecting end of the inlead.

The are tube contains a quantity of mercury which is substantially entirely vaporized during operation of the lamp and which at such time exerts a pressure in the range of l to 15 atmospheres. A quantity of sodium iodide is provided in excess of that vaporized at the operating temperature of the arc tube which is not less than 500 C. at any place. Thallium iodide and indium iodide may also be provided, preferably in the proportions disclosed in US. Pat. No. 3,384,775, Ishler et al. The coolest region of the arc tube during operation are the ends and to insure that they do not drop below 500 C., a heatreflective coating indicated by speckling may be applied to the ends and to the adjacent portions of the pinch seals. Also as a heat conservation measure in the smaller sizes of lamps, such as the 400-watt size, the interenvelope space is evacuated. In the large sizes of lamp such as the 1,000-watt size illustrated, such evacuation is not necessary.

The are tube is supported within the outer jacket by a divided mount. The lower mount section at the dome end comprises a pair of laterally extending support rods 21, 22 which join together at their lower ends to form a U. A metal band 23 is wrapped around the wide pinch seal and consists of two metal straps spot-welded together at the edges of the pinch seal and welded to the support rods at their ends. The weld spots are indicated by small x's in the drawing. The lower ends of the support rods are restrained by transverse springy members 24, 25 whose ends bear against the tubular outer end 4 of the jacket. Pinch seal 18 is provided with blind notches or funnel-shaped cavities 26, 27 in its end which accommodate the ends of right angle braces 28, 29 attached to the rods, as also shown in FIG. 2. The blind notches form protuberances in the flat faces of the pinch seals and the metal band 23 is pulled up snugly against these protuberances. The protuberances formed by the blind notches prevent band 23 from sliding outward off the end of the pinch seal while the right angle braces prevent the band from sliding inward on the pinch seal.

The upper mount section at the base end comprises a pair of longitudinally extending support rods 31, 32 joined together at their upper ends and welded to stiff inlead 8. Springy members 30 bear against the neck portion 5 of the jacket and maintain the support rods in place. A metal band 33 wrapped around the pinch seal, also consists of two straps spot-welded together at the edges of the pinch seal and also welded to the support rods at their ends. Similarly, right angle braces 34, 35 have their ends accommodated in the blind notches 36, 37 in the ends of pinch seal 17.

The upper or base end mount section serves as electrical connector from the base to main electrode 13 at the base end of the arc tube, the connection being effected through wire 38. The connection to main electrode 14 at the opposite end of the arc tube is made through a long curving wire 39 which may be of relatively light weight since it is not required to provide any mechanical support to the arc tube. Preferably it is bent or curved away from the arc tube in order that it may subtend a smaller angle at the arc tube and thereby reduce the amount of light and ultraviolet radiation obstructed. Starting electrode 19 is connected to main electrode 14 at the opposite end of the are tube by a current-limiting resistor 40. A thermal switch 41 is provided consisting of a strip of dissimilar metals bent to a U-shape and welded at one end to the inlead of main electrode 13. As the lamp warms up, the U-shaped piece opens out and its free end engages the inlead of starting electrode 19. The starting electrode is thereby connected to the adjacent main electrode during operation of the lamp, as taught in U.S. Pat. No. 3,226,597, Green, in order to prevent electrolysis of halide salts while yet in liquid form prior to vaporization.

A weakness to which divided amounts are particularly susceptible is lateral displacement or cocking of the arc tube relative to the divided mount sections, particularly at the dome end mount section which is merely springily restrained in the end of the outer bulb or jacket, as shown at lain FIG. 3. The same problem is encountered when the dome end mount section engages an inwardly turned dimple in the end of the jacket, as shown in copending application Ser. No. 594,220, filed Nov. 14, 1966, now U.S. Pat. No. 3,409,790, by Klaus Gottschalk, entitled Arc Tube Mounting and similarly as signed. The thin metal bands 23 and 33 would be quite insufficient by themselves to prevent such lateral cocking. in some lamps presently being manufactured commercially, it has been attempted to overcome this problem by means of relatively heavy sheet metal nose pieces which are clamped over the ends of the pinch seals. Such a structure is expensive to make and difficult to assemble onto the arc tube without breakage.

Our invention provides a much lighter and more economical structure which achieves the purpose at lower cost and which is much easier to assemble. Misalignment is prevented by the engagement of the right angle braces in the notches and also by the interlocking of the bands with the notch protube rances against which the bands are drawn by the right angle braces. Cocking is absolutely prevented by the fact that one end of the band engages one notch protuberance as the brace on the opposite side seats in the other notch. The right angle braces allow sufficient play or give to resist blows or shocks to the lamp. At the same time, the braces are readily bent for adjustment during assembly to allow for manufacturing tolerances. ln tests of large numbers of lamps having divided mounts according to the invention, they have withstood all the usual shock and drop tests to which lamps of this kind are customarily subjected.

We claim:

1. An electric lamp of thejacketed high intensity type comprising a vitreous outer envelope enclosing a quartz arc tube, said envelope having inleads and a base connected thereto at one end, said are tube having an axially projecting wide pinch seal at each end provided with axially outwardly directed blind notches in each corner, a divided mount supporting said are tube within said envelope comprising two pairs of longitudinally extending support rods, a metal band clamped around each pinch seal and fastened to one of said pairs, one pair of support rods being fastened to an inlead at the base end of said outer envelope, the other pair of support rods engaging the opposite end of the envelope, and rodlike lateral braces attached to said support rods and extending into and seating in said blind notches and preventing said bands from sliding in wardly on the pinch seals whereby to maintain alignment of the mount and are tube within said envelope.

2. A lamp as defined in claim 1 wherein said blind notches form protuberances in said pinch seals which are engaged by said bands and prevent them from sliding outwardly on the pinch seals. 

1. An electric lamp of the jacketed high intensity type comprising a vitreous outer envelope enclosing a quartz arc tube, said envelope having inleads and a base connected thereto at one end, said arc tube having an axially projecting wide pinch seal at each end provided with axially outwardly directed blind notches in each corner, a divided mount supporting said arc tube within said envelope comprising two pairs of longitudinally extending support rods, a metal band clamped around each pinch seal and fastened to one of said pairs, one pair of support rods being fastened to an inlead at the base end of said outer envelope, the other pair of support rods engaging the opposite end of the envelope, and rodlike lateral braces attached to said support rods and extending into and seating in said blind notches and preventing said bands from sliding inwardly on the pinch seals whereby to maintain alignment of the mount and arc tube within said envelope.
 2. A lamp as defined in claim 1 wherein said blind notches form protuberances in said pinch seals which are engaged by said bands and prevent them from sliding outwardly on the pinch seals. 